The toxic effects of pyrroles, pyrrole oxides, and pyrrolizidine alkaloids on pulmonary endothelial function will be examined. These agents will also be used to study the development of right ventricular hypertrophy. The effects on liver and cardiopulmonary function of pyrrolizidines present in herbal teas will be studied. A number of pharmacological agents will be tested for their effect on pyrrolizidine-induced right ventricular hypertrophy.